Undergrond continuous impervious wall and method for installing same
This is a division of application Ser. No. 07/196,617, filed May 19, 1988, now U.S. Pat. No. 4,909,674. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an underground continuous impervious wall and a method for installing the same and, more particularly, to an underground continuous impervious wall obtained by disposing an impervious sheet in a gutter, charging a hardening material on the opposite surfaces of the sheet and hardening the same and a method for efficiently installing the same. 
     2. Description of the Prior Art 
     For blocking underground spring water during construction of an underground building or blocking underground water in dam construction works, it has been in practice to construct an underground continuous wall or driving sheet piles and charging a seaming material at the joints. 
     When such prior art processes are carried out for the purpose of blocking water, there are the following problems. 
     (a) Underground continuous walls are usually formed such that they have thicknesses more than necessary. Therefore, unnecessarily elabolate works have to be carried out, and also a large quantity of extra concrete has to be used, thus increasing the installation cost. 
     (b) The process of driving the sheet piles and charging the seaming material at the joints also requires elabolate works and high material cost. 
     (c) It may be thought to form an underground continuous wall having a reduced thickness to reduce the cost of installation. However, there is no machine for excavating a narrow gutter. Even if such narrow gutter could be excavated, the fluidity of concrete would be spoilt to disable completion of a homogeneous underground wall. 
     (d) In view of the reliability of water-blocking, concrete walls are subject to formation of cracks at the time of earthquake, thus spoiling the water-blocking property. In the process using precast concrete panels or sheet piles, foreign materials, e.g., bentonite, are trapped so that it is impossible to obtain the sufficient water-blocking property. 
     An object of the present invention is to provide an underground continuous impervious wall, which can be readily installed, requires inexpensive installation cost and permits construction of an impervious wall having a highly reliable water-blocking property, and a method for installing the same. 
     SUMMARY OF THE INVENTION 
     Such underground continuous impervious wall according to the present invention uses an impervious sheet to partition a gutter and prevent water from passing through the wall. A narrow gutter is excavated in the ground. The impervious sheet is lowered into the gutter to partition the gutter in the width direction. A hardening material is charged onto the opposite side surfaces of the impervious sheet in the gutter and hardened. Thus, an impervious wall with the central impervious sheet is formed. As the impervious sheet, polyethylene sheets and other sheets may be used. It is possible to solidify the mud in the gutter using the hardening material or use soil mortar as the hardening material. 
     There may be thought a plurality of different processes of installing the impervious wall, and also there are several different processes of installing the impervious sheet. 
     First, the impervious sheet is wound on a winding shaft, and then this sheet roll is lowered vertically into the gutter. Then, the sheet is pulled out from the winding shaft to be laid along the gutter. 
     In a different mode of the present invention, a plurality of steel posts are used, and the impervious sheet is stretched between adjacent posts. The posts are lowered into the gutter at a predetermined interval to stretch the impervious sheet. 
     In a further mode of the present invention, the impervious sheet is accommodated in a sheet cartridge to facilitate its stretching in the gutter. The sheet cartridge has a vertically continuous folding groove section formed by a plurality of parallel partition members. The impervious sheet is foldedly accommodated in each folding groove section of the sheet cartridge. The impervious sheet is secured via a space rod detachably provided at a folding portion located at the bottom of each folding groove section in the impervious sheet cartridge. The cartridge with the impervious sheet therein is lowered into the gutter, and the impervious sheet is pulled out to be stretched in the gutter by pulling out the space rods. 
     By winding the impervious sheet on the winding shaft or stretching the sheet between the posts or lowering the sheet in a state accommodated in the sheet cartridge into the gutter, the sheet can be accurately stretched in the gutter. 
     The present invention further concerns a process of connecting together adjacent impervious sheets. Adjacent sheets are provided with respective female and male hooks. The female hook is provided on the trailing edge of the impervious sheet. It is vertically continuous in a rail-like form and has a hook-like sectional profile. The male hook has also a hook-like sectional profile. The male hook is engaged in the female hook of the preceding impervious sheet, and the succeeding impervious sheet is lowered to provide a continuous impervious sheet. 
     The installation works consist of only excavating the gutter, stretching the impervious sheet and solidifying the mud or charging the soil mortar, it is possible to reduce the cost of installation. 
     Since the completed impervious wall includes the impervious sheet intervening between the opposite side wall portions, generation of cracks in the wall due to an earthquake will not be spoiled the water-blocking property, thus increasing the reliability of water-blocking. 
     Since the mud is solidified or soil mortar is charged, the entire underground wall may be made homogeneous. Further, if a portion with a reduced mechanical strength is produced, the water-blocking property can be ensured by the impervious sheet. 
     Further, in case of rock or like earth having satisfactory self-supporting character, the installation cost can be further reduced by using a soft and inexpensive filler, e.g., soil mortar, after the stretching of the sheet. 
     By winding the impervious sheet on the winding shaft or stretching the sheet between the posts or accommodating the sheet in the sheet cartridge, the sheet can be readily stretched in the gutter without possibility of entangling of the sheet 
     Further, by using the female and male hooks for connecting together the adjacent impervious sheets, the sheets can be readily connected together. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The other objects and features of the present invention will become apparent from the following description of a preferred embodiment of the invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a view showing an underground continuous impervious wall; 
     FIGS. 2 to 6 show respectively a process of installing the wall with FIGS. 2 to 5 each having a plan view in I and a sectional view in II and FIG. 6 being a perspective view; 
     FIG. 7 is a perspective view showing an excavating apparatus; 
     FIG. 8 is a perspective view showing an inner mechanism of the apparatus; 
     FIGS. 9 to 12 show respectively a different process of installing an underground continuous impervious wall, each having a plan view in I and a sectional view in II; 
     FIG. 13 is a perspective view showing an impervious sheet used for the same process; 
     FIG. 14 is a plan view showing the impervious sheet in a state of roll; 
     FIG. 15 is a perspective view showing an impervious sheet roll and a post; 
     FIGS. 16 to 18 show respectively a further process of installing an underground continuous impervious wall, each having a plan view in I and a sectional view in II; 
     FIGS. 19 to 24 show respectively a still further process of installing an underground continuous impervious wall; 
     FIG. 25 is a fragmentary perspective view showing an upper portion of a sheet cartridge; 
     FIG. 26 is a fragmentary perspective view showing a lower portion of the sheet cartridge; 
     FIG. 27 (I) and (II) are plan views respectively showing a way of paying off the impervious sheet from the cartridge; 
     FIG. 28 is a perspective view showing the impervious sheet; 
     FIG. 29 is a plan view showing the same; 
     FIG. 30 is a fragmentary perspective view showing the same; 
     FIG. 31 is a sectional view showing a steel pipe; 
     FIGS. 32 (I) and (II) are plan views respectively showing the use of an impervious sheet packer; 
     FIG. 33 is a view showing a connection of the impervious sheet and a joiner; and 
     FIGS. 34 to 36 show respectively a further process of installing an underground continuous impervious wall with FIG. 34 being a perspective view, FIG. 35 being a plan view and FIG. 36 being a plan view showing a connection of adjacent impervious sheets. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 2 to 6 illustrate the process of installing an underground continuous impervious wall according to the present invention. The process will now be described step by step. 
     (1) Boring 
     A plurality of bores 1 are bored at a suitable interval in the ground. The bores 1 may not have a fixed diameter. It is possible that only a bore 1, in which a guide post 4 of an excavating apparatus A which will be later described is erected, may have an increased diameter. The boring of the bores 1 is performed while charging mud 3. 
     When the boring is done in the ground consisting of rock or like earth having satisfactory self-supporting character, mud is unnecessary, and the boring is possible without water. 
     (2) Excavating apparatus 
     The excavating apparatus A as shown in FIGS. 7 and 8 comprises a guide post 4, a drive unit 5 and a saw unit 6. 
     The guide post 4 is a hollow pillar-like member having an inner space 7. It has a rack 8 formed on one side over the entire length thereof. A hose 9 for pumping out the mud is passed through the space 7, and mud can be withdrawn through an earth inlet 10 formed at the lower end of the guide post 4. 
     The drive unit 5 is vertically movable along the guide post 4. The drive unit 5 is provided on its outer periphery with a plurality of guide rollers 11 in engagement with the guide post 4 so that the drive unit 5 is movable along the guide post 4. The drive unit 5 includes a power unit 12, a control unit 13 and an arm 14 for mounting a saw. In the power unit 12, a hydraulic pressure tank 15 and a motor-driven hydraulic power unit 16 are accommodated. A movable sprocket 17 and a control box 18 are accommodated in the control unit 13. The movable sprocket 17 is in mesh with the rack 8 of the guide post 4. A drive motor 19 is driven by the motor-driven power unit 12 to rotate the movable sprocket 17 so as to move the drive unit 5 vertically. In the control unit 13, a saw drive motor 20 is also accommodated, and a saw drive sprocket 21 mounted on the saw-mounting arm 14 is rotated by the motor-driven power unit 12. A saw drive sprocket 22 is mounted on the end of the saw-mounting arm 14, and an endless saw drive chain 23 is passed round the sprocket 22 and saw drive sprocket 21. 
     The saw unit 6 includes a saw frame 24, a chain 25 and a bit 26. The saw frame 24 has one end rotatably mounted on the saw-mounting arm 14 and rotatable with the saw drive sprocket 22 of the saw-mounting arm 14. The endless chain 25 is rotatably passed round the saw frame 24. The chain 25 has a small width, and it has a plurality of bits 26 secured to its surface constituting the outer periphery of the saw unit 6. The chain 25 is driven for rotation by a chain drive motor 27. 
     (3) Excavation of gutter 
     A gutter B having a small width is excavated using the excavating apparatus A as described above. First, the guide post 4 of the excavating apparatus A is erected in the bore 1. The movable sprocket 17 is rotated by the drive motor 19 of the drive unit 5 so that it lowers the drive unit 5 along the rack 8 of the guide post 4 in mesh with the movable sprocket 17. The chain 25 is driven by the chain drive motor 27 so that the chain 25 of the saw unit 6 excavates the gutter B between adjacent bores 1. Since the saw unit 6 has a small width, the gutter B having the small width can be readily excavated. 
     The excavation is performed while charging the mud into the gutter B. The earth removed by excavation is withdrawn together with the mud through the earth inlet 10 at the lower end of the guide post 4 to be discharged to the outside of the gutter B through the hose 9. 
     When excavation is difficult, the saw unit 6 is turned to change its angle by driving the saw drive motor 20 and through the saw drive sprocket 21, chain 23 and sprocket 22. 
     When excavation is done to the same depth as the bore 1, the orientation of the saw unit 6 in the excavating apparatus A is changed or the guide post 4 is erected in the next bore 1 before resuming the excavation. 
     (4) Stretching of impervious sheet 
     An impervious sheet C is stretched in the gutter B which has been excavated to a predetermined length in the manner as described above. As the impervious sheet C may be used polyethylene sheets or the like. The impervious sheet C is connected to a joint 28 of the already stretched impervious sheet C to partition the gutter B in the width direction. 
     (5) Solidification of mud 
     A hardening material D is charged into the gutter B to solidify the mud 3. As the hardening material, mortar, concrete or the like may be used. When the mud 3 is solidified, an underground continuous impervious wall having a small width is completed, which has the impervious sheet C intervening between the opposite side wall portions. 
     In the case of rock or like earth having satisfactory self-supporting character, the mud is unnecessary, and excavation without water is possible. After the stretching of the impervious sheet has been completed, soil mortar is charged in lieu of the mud hardener as filler into the gutter. 
     (6) Other process 
     FIGS. 9 to 15 show other process, in which the impervious sheet C is lowered in a state wound on a winding shaft into a gutter 1. 
     One edge of the impervious sheet C is bonded over the entire length to an elongate bar-like sheet joiner 30. To the other end of the sheet C is bonded an elongate sheet joiner 31 having a C-shaped sectional profile. The impervious sheet C has a pocket-like packer 32 sewed to it near the sheet joiner 31. (FIG. 13) 
     This impervious sheet C is wound on a joiner 33 serving as a winding shaft. The joiner 33 is elongate, and it has rotatable rings 34 each tied to each of the upper and lower ends. Each of the rings 34 has a wire-mounting projection 35. The joiner 33 is fitted in the sheet joiner 31 having a C-shaped sectional profile. The impervious sheet C is wound on the outer periphery of the joiner 33, as shown in FIG. 6. 
     Wires 36 are tied to the respective wire-mounting projections 35 of the joiner 33 and passed round shieves 38 in a cylindrical post 37. The wire 36 is stretched upwardly along the post 37 (FIG. 15). 
     The impervious sheet C is lowered into the gutter B. The impervious sheet C wound on the joiner 33 and post 37 are lowered into the gutter B. The impervious sheet C and post 37 are lowered at a fixed distance from each other. If there is an impervious sheet C which has already been stretched, the newly lowered impervious sheet C is connected to the preceding one by connecting the sheet joiner 31 to the joiner 33 of the preceding one (FIG. 9). 
     The joiner 33 serving as the winding shaft is pulled toward the post 37 by pulling the wires 36 stretched upwardly along the post 37. The impervious sheet C is paid off by displacing the joiner 33 so that it is stretched in the gutter B to partition the gutter B in the width direction thereof. (FIG. 10). 
     The gutter B is partitioned by charging water or air into the sewed packer 32 of the impervious sheet C (FIG. 11). 
     A hardening material, e.g., mortar or concrete, is charged into the mud 3 in the gutter B partitioned by the packer 32 to solidify the mud, thus obtaining the impervious wall (FIG. 12). 
     After the mud has been solidified, the post 37 and joiner 33 are pulled out from the gutter 1. 
     In the case of rock or like earth having satisfactory self-supporting character, the mud is unnecessary, and excavation without water is possible. After the stretching of the impervious sheet has been completed, soil morter is charged in lieu of the mud hardener as filler into the gutter. 
     FIGS. 16 to 18 show a further process, in which the impervious sheet C is lowered in a state stretched between posts into the gutter. 
     As posts 40, it is possible to use H shape steel. The post 40 is secured to either left or right end of one impervious sheet C. Fasteners 41 are tied to the opposite ends of the sheet C over the entire length. A pocket-like packer 42 is sewed to the impervious sheet C near the post 40. A plurality of impervious sheets C are tied to one another by the fasteners 41. 
     The impervious sheet C is lowered in a folded state together with the post 40 into the gutter B. A require number of impervious sheets C corresponding to the length of the gutter B are paid off to partition the gutter B in the width direction thereof. 
     Further, additional impervious sheets C are tied together by the fasteners 41, as shown in FIG. 18. 
     FIGS. 19 to 33 show a still further process, in which the impervious sheet is lowered in a state accommodated in a sheet cartridge into the gutter B. 
     In the Figures, reference numeral 60 designates the sheet cartridge. The cartridge 50 consists of a base 51 having a semi-circular sectional profile. Inside the base 51, a vertically continuous folding groove 53 is formed by a plurality of parallel partition members 51. A bar-like guide member 54 is secured to the free end of each partition member 52. The cartridge 50 has a bottom 55 formed at the lower end and consisting of an expandable metal. Partitioning retainers 56 are secured to the bottom 55 near the base 51 to partition the folding groove 53. 
     In the Figures, reference symbol C designates the impervious sheet, e.g., a polyethylene sheet. As shown in FIG. 11, the impervious sheet C has an elongate bar-like sheet joiner 58 secured to one end and a sheet joiner 59 having a C-shaped sectional profile and secured to the other end. The impervious sheet C also has a pocket-like cover 60 bonded to it near the sheet joiner 59. An elongate sac-like packer 61 is inserted in the cover 60. 
     The above impervious sheet C is accommodated in a folded state in the folding groove 53 of the sheet cartridge 50. Each folded portion of the impervious sheet C is located at the bottom of each section of &amp;he folding groove 53. In the folded portion, a space rod 62 is provided between each partitioning retainer 56 and the base 51 to prevent detachment of the impervious sheet. 
     The impervious sheet C is lowered into the gutter B. At this time, the impervious sheet C is lowered in a state secured to the sheet cartridge 50 into the gutter B. The elongate joiner 58 is fitted in the sheet joiner 59 of the impervious sheet C (FIG. 33). A plurality of wires 64 are tied to the joiner 58, and they are passed round shieves 66 in a post 65 consisting of a steel pipe to be pulled upwards (FIG. 31). 
     When lowering the sheet cartridge 50 into the gutter B, the post 65 is also lowered into the gutter B such that it is parallel to the cartridge (FIG. 20). If there is an already stretched impervious sheet C in the gutter B, the new pervious sheet C is lowered with its sheet joiner 59 engaged in the sheet joiner 58 of the preceding sheet, whereby the two sheets C are joined together by the sheet joiners 58 and 59. 
     After the sheet has been lowered, the wires 64 passed through the post 65 are pulled to pull the lowered impervious sheet C. At this time, the space rods 62 are withdrawn one by one so that the impervious sheet C is ready for being paid off from the folding groove 53 as shown in (I) and (II) in FIG. 27. 
     The impervious sheet C is stretched in the gutter B in the manner as described above such that it partitions the gutter B in the width direction thereof (FIG. 22). 
     Then air or water is charged into the packer 66 of the stretched impervious sheet C to partition the gutter B. Then the hardening material D is poured into the gutter B partitioned by the packer 66 to solidify the mud 3. 
     FIGS. 34 to 36 show a method for connecting the impervious sheets C. A bar-like weight 70 is secured to the lower end of the impervious sheet C over the entire length of the lower end. A plurality of impervious sheets C are introduced one by one into the gutter B. The trailing end of the preceding impervious sheet C is provided with a vertically continuous female hook 71 having a hook-like sectional profile. To the leading end of the impervious sheet C is secured a male hook 72 having a hook-like sectional profile. In this embodiment, a plurality of male hooks are provided, but it is also possible to provide a single, vertically continuous hook. 
     The impervious sheet C is lowered in a state suspended from a bar-like hanger 73 into the gutter B by a crane or the like. When introducing the impervious sheet C subsequent to the preceding impervious sheet C into the gutter B, the male hook 72 of the succeeding impervious sheet C is engaged in the female hook 71 of the preceding impervious sheet C. 
     In the above way, a plurality of impervious sheets C are introduced continuously into the gutter B to partition the gutter B in the width direction thereof. 
     When solidifying the mud, the gutter B is partitioned by driving locking pipes 74 in order that a given solidification range is provided lest the mud should be solidified in range where there are the hooks 71 and 72.